An Henbest reduction, followed by the preparation of a silyl enol ether and oxidation in situ with m-CPBA has led to the neurosteroids 3α-hydroxy- and 3α,21-dihydroxy-5α-pregnanolones. Using testosterone as starting material, a new short synthesis of an aromatase inhibitor, 4-OHA, has been achieved through hydroboration/oxidation followed by a Swern type oxidation and epimerization. Another aromatase inhibitor, androst-4-ene-3,6,17-trione, has been efficiently prepared using PCC on montmorillonite K10, under ultrasonic irradiation.
Campos Neves, A. S., Sá E Melo, M. L., Moreno, M. J. S. M., Tavares Da Silva, E. J., Salvador, J. A. R., Da Costa, S. P., & Martins, R. M. L. M. (1999). Improved syntheses of aromatase inhibitors and neuroactive steroids efficient oxidations and reductions at key positions for bioactivity. Tetrahedron, 55(11), 3255–3264. https://doi.org/10.1016/S0040-4020(98)01138-7